The TROPOMI satellite: new exciting possibilities for monitoring natural airborne hazards

by EUNADICS-AV consortium, 22 January 2018

Satellite measurements play a crucial role in global monitoring of natural airborne hazards like volcanic eruptions, wildfire, and dust storms. Since the beginning of this century, several satellite instruments that monitor the atmosphere have shown to provide invaluable information on the location and magnitude of such events. These measurements are an integral part of the aviation advisories that are issued by Volcanic Ash Advisory Centers (VAAC) around the world.

Some of these satellite instruments like OMI, GOME-2, and OMPS, measure reflected solar radiation, which can be used to detect volcanic ash, sulphur dioxide (SO2), smoke particles and desert dust. These satellite instruments provide several daily worldwide snapshots of these airborne hazards.

On 13 October 2017, ESA launched the Sentinel-5P satellite, which is considered to be the first of the next generation of atmospheric Sentinel satellites. The only instrument on board, TROPOMI, builds on the heritage of OMI, SCIAMACHY and GOME-2. The TROPOMI instrument will provide more accurate measurements and at a much better spatial resolution than the currently existing instruments.

The first images and snapshots of the atmosphere obtained with this new satellite were recently presented during the by ESA organized TROPOMI First Light Event.

Even though the first data currently represent unverified quality since the satellite instrument still needs to be fully calibrated and validated, results reveal that TROPOMI indeed provides a leap forward in terms of spatial resolution, sensitivity, and accuracy. While the OMI and GOME-2 satellite measurements will continue to be useful for monitoring hazards, TROPOMI provides many more details on small spatial scales.

Figure 1 below shows some of the preliminary first results of ash and SO2 of the volcanic eruption of the Agung volcano on Bali, Indonesia, observed on 27 November 2017.



The comparison of SO2 between GOME-2 and TROPOMI clearly shows that GOME-2 can measure this relatively small SO2 cloud, but that TROPOMI provides significantly more and finer details.

Figure 2 shows the TROPOMI preliminary absorbing aerosol index (AAI) for the recent California wildfires (12 December 2017), while figure 3 shows the TROPOMI AAI for a smog episode over norther India on 10 November 2017 and the corresponding VIIRS RGB image. The AAI is an important indicator of volcanic ash, smoke, and desert dust.

These first images from TROPOMI offer a taste of the high spatial resolution of TROPOMI and the details that can be observed, and the quality of the data. Once the satellite has been commissioned, it will map the entire planet every day with unprecedented accuracy. TROPOMI is therefore expected to become an important asset of the EUNADICS-AV project. Public accessibility to all TROPOMI data is expected by late spring 2018.

Figure 2. The (preliminary) TROPOMI absorbing aerosol index on 12 December 2017 for the recent California wildfires. Source: KNMI.

Figure 3. Smog episode over northern India on 10 November 2017 as observed by NPP-VIIRS (RGB image; upper plot) and the preliminary TROPOMI absorbing aerosol index (lower plot; color coding similar to figure 2). Source: NASA worldview (SUOMI NPP-VIIRS) and KNMI.